booth



March 5, 1957 w. K. BOOTH METHOD OF COOLING AND CONDITIONING BREAD Filed June l. 1951 IN V EN TOR. h//LL /A/V /K Boor/1' y Hfs ,4 rmt/V616 MRR/5 /fc/s; F65 @NM1/W75 @f United States Patent() METHOD F COOLINGl AND CONDITIONING BREADr William K. Booth, Pasadena, Calif., assignor, by mesne assignments, to rCapitol Products Corporation, Mechanicsburg, Pa;, a corporation of Pennsylvania Application June 1, 19.51, Serial No. 229,410

2 Claims. (Cl.13420) The present invention relatesin general to a method ofv and apparatus for cooling bakery productsiafte'r bak-` ingv and, more particnlarl`y, to a method of and apparatus for cooling loaves of bread.

After loaves of bread have been bakedthe`y'ar eA removed from the baking pans and cooled before being processed further, cooling of the loaves being essential for at least two reasons; First, when the loaves of bread are removed from the baking pans, they have insutlicient structural strength to withstand the forces applied thereto by slicing and/ or wrapping machines, for example, andv such moisture being exuded by theloaves during cooling..

Otherwise, such moisture would condense on the inner surfaces of the wrapping paper 'and'.would ultimately be absorbed bythe loaves to render them soggy. 'I'he customary practice is to cool the loaves. to an internal temperature of the order of magnitude of 90 F. to 110 F.

before processing the loaves further, although it will be understood that the present invention is not limited to this particular range of temperatures.

In large bakeries employing travelling ovens, the loaves of bread are removed from the baking pans as the latter arrive at the discharge endA of the oven and are placedon shelves or trays which are continuously'conveyed through a cooling chamber, the trays ordinarily being pivotally suspended from conveyor chains, or the like, so that the loaves of bread may be dumped from the trays after cooling by rotating or tilting the trays into dumping posi.- tions. In order to cool the loaves in a reasonable length of time, it isconventional to circulate cooling airthrough the cooling, chamber, a cooling timeof approximately one and one-half hours being more or less,standard. In

other words, a period of about one and one-half hours is required for each cooling tray to pass through the cooling chamber.

In they past, in order to reduce the cooling time to a reasonable value, it-was ,necessary to refrigeratek the cool-l ingl air under, conditions of highjatmospheric temperatures, particularly where the atmospheric humidity was.

Moreparticularly',` refrigeration ofthe co'ol-` ing jair has been regarded-"as essentiallwhenever theA atmospheric relative humidity approaches-570%" witlrian` atmospheric temperature-of-70` Ff, or'more. Asris well alsohigh.

known inthe art, refrigerationsystemsifor 'breads cooling-installations are expensive; both asiiregardsiinitial costs and operating costs, because-V of the relatively large volumes of air-that-they must-handle.

In view-of the foregoing, an important object^of theV invention is to providea breadA coolingmethod-and"apsparatus -which avoids manyA of -the f disadvantages of? prior practice by eliminating-anynecessity forrefri'geratinglxthe cooling air, atleastlin most areas ofthe'worltr ffice I accomplish the foregoing by evaporative cooling `of the loaves of bread with air of` high temperature, and humidity flowing over or past the loaves atta high velocity. More particularly, I accomplishthe foregoing byV employing cooling air having a dry bulb temperature of.A fromabout 5 F. to about 20 F. less than the' final-internal bread temperature and having` a relative humidity of atleast and by flowing the cooling air; of such temperature and humidity over or past the loaves of bread at a velocity of at least 150 feet per minute. Preferably, the dry bulb temperature'of thecooling air is between approximatelyS F. and 10 F. below the final internal bread temperature, and the velocity of thecooling air is approximately 250 feet per minute. The relative humidity of the cooling air is preferably aroundv to and may approach 100%.

An important feature of the present invention is that it cools the bread to a specied internal temperature in a period of time of less than the one and one-half hour period discussed previously, and results in loaves of bread having crusts of excellent quality, i. e., tender and neither too dry nor too moist. More particularly, the quality of the cooled product is at least equal to, and in many instances superior to, that of bread cooled in refrigerated installations used heretofore, such excellent resultsbeing obtained under temperature and humidity conditions for the coolingair which have heretofore been regarded as entirely .too hot and humid, by owing the` airpast the loaves of bread at a high velocity.

An important advantage of thel present invention is,vv

that the Iforegoing -conditions of temperature and humid ity for the cooling air may be attained readily with equipment which may be installed and operated very economi.- cally as compared to refrigeration systems. For example, in the southwestern section of the continental United States where the air is normally hot and dry during the.

summer, the foregoing temperature and humidity conditions for the cooling air may be attained readily merely `by Ahumidifying the `air by a spraying process, or otherternal temperature of approximately F. with air of such dry bulb temperature and relative humidity in about one and one-quarter hours by circulating the air past the loaves of bread at a velocity of about 240 feet per minutc, i. e., at a velocity substantially equal to the preferred velocity discussed previously.

The crusts of the loaves after cooling under such conditions were tender and of excellentquality.

As will be apparent, similar conditionsv of temperature and humidity for the cooling air'may readily be obtained in other areas. For example, the atmospheric temperatures and relative humidities in various parts'of the' continental United States,'such as in the eastern and middlewestern sections thereof, are frequently within the desired ranges during the summer. During other seasons of the year, and in colder locations-the desired temperatures andfrelative humidities may oeobtained readily `merely by-humidifying and heating the air as required. Similarly, thedesired temperatures and humidities may be'obtained in' substantially allai-eas of ,the world merely by heating.

orative` cooling 'of' the AVair,u which frequir'es 'no` expensive equipment:

Thus;-by-employing cooling airtof -high"tempetature and humidity, which conditions are readily attainable, and by circulating the air past the loaves of bread at a high velocity to compensate for the high temperature and humidity of the cooling air, the present invention permits evaporative cooling loaves of bread and with inexpensive and economically operated equipment, which is an important feature. It will be understood that the cooling air velocity must be sufhciently high to enable the relatively hot air to cool the loaves of bread in a reasonable length of time and rnust be sufficientlyY high to avoid complete saturation of the air by the moisture evaporated from the loaves of bread. in other words, the velocity of the air must be sufficiently high to prevent the air temperature from attaining the temperature of the bread, and to prevent the relative humidity from attaining 190%. I have found that the velocity of the air must be at least l() feet per minute and, preferably, of the approximate order of magnitude of 250 feet per minute. The air velocity maybe increased considerably above the latter value, although,V as a practical matter, the air velocity should not exceed 500 feet per minute.

As will be discussed in more detail hereinafter, the foregoing values of cooling air velocity are based on the volumetric rate of flow of air through the cooling chamber in cubic feet per minute divided by the crosssectional area of the cooling chamber, without making any allow-v ance for the effects of and the area reductions offered by the obstructions in the cooling chamber, such as the cooling trays, the loaves of bread carried thereby, and the like. Consequently, theactual mean velocity of the air, taking into account the effect of obstructions in the cooling chamber, would be somewhat higher than the values discussed previously, and would be subject to local variations because -of the effects of the obstructions. Consequently, it must be understood that the values for cooling airvelocity used herein are, as hereinbefore indicated, based on the volumetric flow rate divided by the cross` sectional area of the stream of cooling air.

) An important4 object of the present invention is to provide a method and apparatus wherein the general ow of loaves of bread through the cooling chamber is in a direction opposite to the direction of ow of tht-:cooling air therethrough so that the loaves are exposed to progressively cooler cooling yair as they are cooled. In other words, the incoming bread is exposed to cooling air whose temperature has been increased by heat extracted from previously cooled loaves, and then is exposed to progressively cooler air as the temperature thereof decreases. t

l prefer to accomplish the foregoing by dividing the cooling chamber into two cooling zones, the cooling air being delivered to the first cooling zone and owing therethrough into the second cooling zone by way of interconnecting passage, the loaves of bread being cooled being conveyed in the opposite direction, i. e., being delivered to the second cooling zone mentioned and then being conveyed into the first cooling zone.

' Another object is to provide a generally horizontal cooling chamber which is divided into the aforementioned coolling zones by `a generally horizontal baflie or partition extending substantially the entire length of the cooling chamber, the baille being spaced from one end of the cooling chamber to provide an interconnecting passage between the two cooling zones and to provide a passage through which the trays of bread may be conveyed from the second cooling zone into the tirst. Preferably, the first cooling zoneinto which the cooling air is introduced initially s below this bathe, the second cooling zone into which theloaves of bread are introduced initially being above thebaie. The cooling conveyor carrying the trays of bread preferably is provided with a plurality of generally horizontal runs some of which are above the bathe o lpartition and the rest of which are located therebelow. Preferably, the baflie is located at a level above the bottorn .ofthe cooling chamber equal to approximately onehalf to three-quarters of the height of the cooling chamber so that the volume of the lower cooling may range from a value approximately equal to that of the upper cooling zone to a value of approximately three times 5 that of the upper cooling zone.

Another important object iof the invention is to pro vide proportioning means for mixing, in a mixing chamber, exhaust air taken from the upper cooling zone with fresh air taken from an outside source, the resulting mixture subsequently being humiditied and/or heated to bring its temperature and humidity yto thedesired values before introducing it into the lower cooling zone. Another object is to provide such a proportioning :means capable of varying the proportions of the l5 exhaust air and the fresh air entering the mixing zone between 0 and 100%. In 4other Words, only fresh air can be delivered to the lower zone of the cooling chamber by the proportioning means, or only air exhausted from the upper zone of the cooling chamber may be delivered to the lower zone by recirculation, or any desired proportions of the two may be employed. For example, when operating at night, or at any time when the outside air temperature is low, it is desirable to employ a partially or completely closed system to avoid having'to' heat the cooling air excessively. The proportioning means permits operating the installation as a partially or completely' closed system in this manner, which is an important feature.

' Another object is to provide a control system which controls the proportioning of fresh air with exhaust air, the humidication lof the resulting mixture and `the heating of the resulting mixture to provide the cooling air delivered to the lower zone of the cooling chamber with the desired relative humidity and dry bulb 4tem- 3) perature. Another object is to provide means for heating the water used to humidity the cooling air when the cooling water temperature is low, or when the -temy perature of the air delivered to the humidifying zone is' particularly low.

invention, together with various other objects and advantages thereof which will become apparent, may be attained with the exemplary embodiment of the invention which is illustrated in the 'accompanying drawing,

and which is described in detail hereinafter. Referring to the drawing:

IFig..l is a diagrammatic plan view of one embodi-v illustrated therein includes an elongated cooling chain,-vx

ber 10 which is disposed horizontally on a iioor 11, or the like. A horizontal partition or baie 12 extends laterally across the interior of the cooling chamber 10 and extends longitudinally thereof to divide the cooling chamber into a iirst, lower cooling zone 13 and a second, upper cooling zone 14. Cooling air is introduced into the lower zone 13 of the cooling chamber 10 through an inlet 15 at one end of the 'lower cooling zone and flows substantially horizontally through the lower cooling zone to a passage 16 at the other end thereof which connects the upper cooling zone 14 to the lower coolingzone. "From the upper cooling zone 14, the cooling air is discharged .through one or the other, or both, of two outlets 17 and 18 having exhaust fans 19 and 20 therein,-

The cooling chamber 10 isprovicled with 'twoghorhf *0 `The foregoing objects and advantages of the present4 zontally spaced, vertical walls 26fand'271which'extend horizontally across the cooling chamber and which .ex-t tend vertically from the bottom of the cooling chamber substantially to the top thereofthe wall. 27 cooperating with one end of the horizontal bale'12. to provide the passage 16 interconnecting the upper and flower cooling zones. The walls 26 and'27 are connected. along their upper edges by walls forming a discharge chute 28 for cooled loaves of bread, this discharge chute` leading to a discharge conveyor 29 extending crosswise of' the -cooling chamber 10. The wall 26 cooperates with the adjacent end wall of the cooling chamber to provide a loading chamber 39 for loaves of bread to be cooled,

this loading chamber extending .downward into -a pit 31- in the iloor 11 in the particular construction illustrated. The loaves of bread to be cooled are delivered to the cooling chamber 10 by a loading. conveyor 32 which extends crosswise of the cooling chamber 10, a pusher or ram 33 being provided to. feed the loaves of bread from the loading conveyor 32 into the loading chamber 3i) through an opening 34 in the corresponding end Wall of the cooling chamber.

The loaves are pushed through the loading opening 34 by the ram 33 onto trays or shelves 35l 'on a cooling conveyor 36 which operates in timed relation with the ram. Each tray 3S is adapted to receivea plurality of loaves of bread and is preferably pivotally suspended from the cooling conveyor 36, which may comprise a pair of spaced, parallel chains, for convenience in dumping the loaves of bread from the trays after cooling, as will be discussed in more detail hereinafter. The cooling conveyor 36 is trained around rotatable elements, such as sprockets, which guide the cooling conveyor and the trays carried thereby through the cooling chamber to and which provide a plurality of horizontal runs in the lower and upper cooling zones 13 and 14, the direction of movement of the cooling conveyor being indicated by the broken-line arrows 37. Preferably, the horizontal baille 12 .is so disposed between two of the runs of the cooling conveyor 36 that there are several runs above and below the bale. Preferably, the elevation of the baie 12 above the bottom of the cooling chamber 16 is equal to from about one-half to threequarters of the height of the cooling chamber so that the volume of the lower cooling zone 13 ranges from a value about equal to that of the upper cooling zone to -a value approximately three times that of the upper cooling zone. As will be noted, the cooling conveyor 36 moves'from the upper cooling zone 14 into the lower cooling zone 13 through the interconnecting passage 16. After a given tray 35 on the cooling conveyor 36' has passed-all the way through the upper and lower cooling zones 14 and` 13, it is conveyed upwardly over the discharge chute 28 and, at this point, it is rotated into a tilted position so that the loaves of bread slide therefrom into the discharge chuteY and downwardly onto the discharge conveyor 29, which conveys them to slicing and/or wrapping machines, or the like.

As will be noted, the cooling air firstv enters the lower cooling zone 13 and flows therethrough into the upper cooling zone 14, from which it ows out of the cooling chamber 1G through either or both of the outlets 17 and l. Conversely, general movement ofthe loaves of bread being cooled is from the upper coolingv zone14 to the lower coolingfzone 13 so that, in general, there is coun tercurrent movement of the bread and the cooling air. ln other words, initially, the hot bread is exposed to cooling air which has been heated by loaves introduced earlier, and, as the loaves of bread cool, they are exposed to progressively cooler air in the lower cooling zone 13. Such countercurrent ow of the cooling air and the loaves of bread being cooled results inmore effective utilization of the cooling air, which is an important feature. Also, the employement of thebafe 12 Vfor .separating the' two cooling zones coniinesthecooling air cooling air exists throughout .the entire lower cooling.

zone 13.

Considering thev manner in which the cooling air is.

conditioned and delivered to the inlet l15 of the cooling chamber 16, the inlet 15 communicateswith the outletof a blower 40. The capacity of the blower 40 -is so related to the cross-sectional area of the lower cooling zone.

13 .thatzthe desired velocity ofA the` cooling air through thel lower cooling zone is obtained. As previously ,inf dicated, the values set; forth for the velocity of the cool`-` ing air are based'onv the` volumetric ratei of ow through:V the lower cooling zone 13 divided by the `cross-sectional` area: of the lower-cooling zone, without any allowancefor such obstructions in the lower cooling yzone as the cool ing conveyor'- 36, the trays 35, the loaves of bread'on the trays, .and therlike. lu other words, the air velocityV values. herenbefore recited merely represent. the output of the blower 40 divided by the cross-.sectionalarea of the lowercoolingzoneu13 without any allowance forv the obstructions' in the lower cooling zone.

The intake yof the blower40 communicates through a duct 4I with a conditioning chamber or zonef 42 in which they cooling air is brought'to the desired dry bulb temperature and relative humidity. In the conditioning chamber .42 isa heater 43 through which the cooling air ows. For example, the heater 43 maybe a steam radia-4 tor supplied with steam through a pipe 44 having a con,y

trol valve 45- therein on; a control panel indicatedA gen'- erally` by the numeral 46. Also disposed in the condi#v tioning chamber 42 isV a humidifying means which is exemplified as a spraying means Stlffor spraying water, into the stream of cooling air upstream fromthe heater 43- as the stream of cooling air flows through thecondi-k tioning chamber 42. The spraying means is suppliedv with water through a .pipe 51 having a control valve 52'.'

therein on the.- control panel- 46. It willbe understood that. the water delivered to the spraying means 50 may. For example, freshl water may be continuously supplied to the spray-f be obtained from anysuitable source.

ing. meansS()l through the waterv pipe 51, or, at least kpart of. the-water` supplied to the sprayingy means may be obtained .from a sump 53 below the spraying means, such" sump 4,serving to collect the water which is not takenrup by the cooling air stream. If desired, the proportions ofthe water'taken from the'. sump 53 and fresh water taken from an outside source may be controlled' in any suitable manner, not shown, to provide the desired water temperature, the proportion of fresh water usedbeing increasedv as the water temperature in the sump increases and vice versa. Also, in the event that extremely cold water is employed, or in the event that the cooling air entering the conditioning chamber is rather cold, steam maybe added to the cooling water tol increase its temperature and/or. to assist in heating the cooling air. For tlns purpose, a steam. pipe 54 is connected to thewater i Ypipe 51 and is controlled by a steam valve 55 on' thereontrol panel 46.' As will be apparent, by suitable manipwlationl of the waterand steam valvesl 52 .and I55, Athe temperature of' the spraywater may be increasedv to any de sired value, dependingupon conditions,

The stream of cooling air delivered to theA conditioning chamber'42 originates in a mixingchamber or zonev 60" which has a fresh air intake 61 and a recirculating-v intake`I 62. The '-former; communicates with an outside. source., such as'tl'i'einterior or exterior of a building in which the inst'allationis located, 'and the latter communicates with theoutlet 18 of the cooling chamber lil. The outlet 18 alsocommunicates with an exhaust passage 63 in which the exhaust fan'20 is disposed. Thus, with this arrangement, the `stream of cooling air delivered to the conditioning chamber 42 from the mixing chamber 66 may include fresh air and recirculated air in various proportions, a proportioning valve means 64 associated with the fresh air intake 61, the recirculating yintake 62 and the exhaust passage 63 being provided to control the proportions. As will be discussed in more detail hereinafter, the proportioning valve means 64 permits mixing recirculated air and fresh air in the mixing chamber 6i) in any desired proportions, ranging from .to V100% of either. In other words, the proportioning valve means 64 permits operating the cooling system as a closed system, an open system, or as a partially closed system.

The principal advantage of this arrangement is that it permits operating the system as a closed system, or a substantially closed system, at night or at any other time when the outside air temperature is low, or when the installation is rst put into operation and is warming up. in this way, excessive heating of the cooling air to bring it up to the desired temperature is eliminated, which is an important feature since it permits more economical operation of the installation. Also, this feature permits a faster warmup of the installation, particularly during cold weather operation.

1 Considering the proportionng valve means 64 in detail, it includes intake shutter means 67 and 68 in the n intakes 61 and 62, respectively, and exhaust shutter means 69 in the exhaust passage 63, each shutter means including a plurality of pivoted shutter elements which are interconnected to operate in unison. The three shutter means 67, 68 and 69 are so interconnected that when the intake shutter means 67 in the fresh air intake 61 is fully open, the intake shutter means 68 in the recirculating intake 62 is fully closed and the exhaust shutter means 69 in the exhaust passage 63 is fully open. Under such conditions, only fresh air is delivered to the mixing chamber 60, all of the air exhausted through the outlet 18 being discharged through the exhaust passage 63 by the exhaust fan 20. Conversely, the three shutter means are so interconnected that when the intake shutter means 67 in the fresh air intake 61 is fully closed, the intake shutter means 68 inthe recirculating intake 62 is fully open and the exhaust shutter means in the exhaust passage 63 is fully closed. Under such conditions, no fresh air is admitted to the mixing chamber 60, the system operating as a closed system under these conditions. For intermediate positions of the three shutter means, fresh air and recirculated air are mixed in variable pro# portions depending upon the positions of the shutter means.

in the particular construction illustrated, the foregoing g v operative relation between the three shutter means 67, 68 and 69 is obtained by connecting a sprocket 71 which drives the intake shutter means 68 to a sprocket 72 which drives the exhaust shutter means 69 through a chain 73 trained around such sprockets. Similarly, a sprocket, not visible in the drawing, rigidly connected toV the sprocket 71 is connected by a chain 74 to a sprocket 75 which drives the intake shutter means 67. Thus, whenever the position of the intake shutter means' 68 is changed, the positions of the shutter means 67 and 69 are changed correspondingly in the relation discussed' theshutter means 63 by a diagrammatic connection 77.v For example, a synchro system may be used, the control 76operating a master synchro, not shown, which, in turn, controls a slave synchro connected tothe sprocket 71.

S Alternatively, any other suitable connection between the control 76 and the shutter means may be employed.

In the illustrative control system shown for the apparatus, aV dry bulb temperature pickup 78 is disposed in the inlet and is connected to a dry bulb temperature indicator 79 on the control panel 46. Similarly, a wet bulb temperature pickup 80 is disposed in the inlet and is connected to Va wet bulb temperature indicator 81 on the control panel. As will be apparent, the dry bulb temperature of the cooling air introduced into the lower cooling zone 13 and the relative humidity thereof can be obtained from the indicators 79 and 81, together with a psychrometric chart. Alternatively, a relative humidity indicator, not shown, may be employed to indicate the relative humidity directly.

Considering the over-al1 operation of the illustrative apparatus disclosed for performing the method of the invention, it will be assumed that the blower is delivering the volume of air required to provide the desired velocity through the lower cooling zone 13. Preferably, the blower is provided with a variable drive means, not shown, to permit operating the system at various air velocities through the lower cooling zone. With the air velocity through the lower cooling zone 13 at the desired value, the relative humidity and dry bulb temperature of the cooling air delivered thereto may be regulated readily by means of the steam valve through which steam is supplied to the heater 43, the water valve 52 through which water is supplied to the spraying means 50, the steam valve through which steam is supplied to the spraying means 50 and the control 76 for the shutter means 67, 68 and 69. Any deviation in the indicated dry bulb temperature and relative humidity from the desired values may be corrected by manipulating one or more of these controls as required.

When the installation is iirst being put into operation, and particularly when the outside air temperature is low, or when the installation is in operation with a low outside air temperature, it is desirable t0 recirculate some or all of the cooling air so as to avoid excessive heating of the cooling air in Athe conditioning chamber 42 to bring it up to the desired dry bulb temperature. On the other hand, if the outside air temperature is high, and particularly if the outside air is dry as well, it is frequently desirable to operate with only fresh air entering the mixing chamber through the fresh air intake 61, such hot, dry air readily being cooled to the desired temperature and humidied to the desired extent by the spraying means 50. As will be understood, when the system is operated as a closed system, the exhaust fans 19 and 2t), and particularly the former, are preferably shut down.

It will be understood that while I have disclosed an apparatus wherein the dry bulb temperature, relative humidity and velocity of the cooling air are maintained at the desired values completely manually, the variables may be controlled in other ways. For example, the relative humidity and dry bulb temperature may be controlled by devices, not shown, responsive to dry bulb temperature and relative humidity. Thus, although I have disclosed an exemplary embodiment of an apparatus of the invention which is capable of performing the method of the invention, it will be understood that various changes, modications and substitutions may be incorporated therein without necessarily departing from the spirit of the invention.

l claim las my invention:

l. A method of cooling loaves of bread in a cooling zone to a desired specilic internal temperature in the range between F. and`ll0V F. after baking, including the steps of: moving cooling air in a stream through said cooling zone at a velocity of the order of magnitude of 250 feet per minute; maintaining the dry bulb temperature of the cooling air upstream from the cooling zone between approximately 5 F. and 10 F. below said desired specic internal temperature; and maintaining the relative humidity of the cooling air upstream from the cooling zone at about 85% to 90%.

2. A method of cooling loaves of bread to a desired specic internal temperature in the range between 90 F. and 110 F., including the steps of: moving air along a path which includes a conditioning zone and a cooling zone with a velocity through said cooling zone between 250 feet per minute and 500 feet per minute, said cooling zone being adapted to receive the loaves of bread to be cooled; adding water and heat to said air in said conditioning zone; and controlling the amounts of water and heat added to said air in said conditioning zone to maintain the dry bulb temperature of the air moving from said conditioning zone to said cooling zone between about 5 F. and 10 F. less than said desired specific internal temperature, and to maintain the relative humidity thereof above about 85% to 90%.

References Cited in the file of this patent UNITED STATES PATENTS 1,753,828 Greer -e Apr. 8, 1930 1,798,781 Brooks Mar. 31, 1931 1,885,142 Reece et al. Nov. 1, 1932 2,008,407 Stoever July 16, 1935 2,073,221 Reece et al. Mar. 9, 1937 2,101,651 Reece Dec. 7, 1937 2,192,348 James Mar. 5, 1940 2,215,193 Reece Sept. 17, 1940 2,257,487 Tenny Sept. 30, 1941 2,275,588 Greene Mar. 10, 1942 2,277,382 Botz Mar. 24, 1942 2,501,898 Haggerty Mar. 28, 1950 2,643,523 Burgess June 30, 1953 OTHER REFERENCES Freihofer Baking Co., by E. C. Pfathause'n, lHeating and Ventilating, January 1942, pages 55 to 57. 

